Reforming followed by hydrodealkylation



1957 c. E. HEMMINGER ETAL 2,780,661

REFORMING FOLLOWED BY HYDRODEALKYLATION Filed Aug. 15, 1951 mqiomd wdohozhwfl a w .0 Rm

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Qttornes REFORMING FOLLOWED BY HYDRODEALKYLATION Charles E. Hemminger,Westfield, and Charles W. Tyson, Summit, N. L, assignors to EssoResearch and Enghieering Company, a corporation of Delaware ApplicationAugust 15, 1951, Serial No. 241,954

4 Claims. (Cl. 260-672) The present invention relates to. improvementsin hydrodealkylation of hydrocarbons and in particular itrelates toimprovements in the performance of this process employing the fluidsolids technique.

Heretofore and prior to the present invention, it was oldto hydroformnaphthas to convert the naphthas therein contained to aromatics and atthe same time to cause some 'isomerization of normal hydrocarbons toform branched chain parafiinic hydrocarbons. This type of operation iscarried out, at least commercially, in the presence of fixed beds ofcatalyst. Furthermore, in this type of operation the feed stock was notonly one which contained appreciable quantities of naphthenichydrocarbons but also boiled within a limited range, namely, 200-360 F.One aspect of the present invention involves. the. use as a feed of ahigher boiling material which in onephase of the. process is hydroformedandthe. higher boiling portions of the. hydroformate. product arevdealkylated to form aromatics of lower boiling range.

One. object of the present invention, therefore, is. to producerelatively low boiling aromatics, such. as. benzene,

.toluene, and various xylene isomers from a relatively high boilingnaphthenic naphtha.

Another object of the. present invention is toproduce gasolines ofincreased volatility from light gas. oils, which gasolines possess ahigh octane rating.

Another object of the present invention is to carry out thehydrodealkylation of products from a hydroforining operation in a systemwhich is substantially self-sufliicient 2,786,651 Patented Feb. 5, 1957ice alkylated aromatics is carried out in the presence of a fluidizedbed of powdered inert material, such as sand, pumice, silica, coke,etc., or active cracking materials as activated alumina, silica,alumina-silica or acid treated clays may be employed with heavier orhigher boiling feed stocks. A naphthenic naphtha boiling within therange of from, say, 250-450 F. enters the present system through line 3,is charged to a furnace 3a where it is vaporized and heated to atemperature of about 1000 P. and thereafter charged into thehydroforming vessel 1 which contains, as previously indicated, afluidized bed C; of powdered hydroforming catalyst. This catalyst powderranges in size from about 100 to 400 mesh or any other suitable sizeadapted for fluidization, and the gasifor-m material moves through thebed at a superficial velocity of from about 0.2 to 0.7 ft. per second.As usual, the vessel containing the fluidized bed of catalyst isprovided with aforaminous member G which acts as a gas distributingmeans for hydrogen-containing gas, which is fed from line 4 to furnace 5where it is heated to a temperature of 1150 F. or thereabouts, andthereafter charged via line 6 into the bottom of the reactor vessel 1where it passes upwardly through the foraminous member or grid G intocontact with the bed of catalyst .C. In connection with the oil feed, itis to be noted, as shown in the drawing, that the feed oil is fed to apoint above, the grid G. Under conditions more fully set forthhereinafter, the desired conversion takes place and the product issuesfrom the dense fluidized bed of catalyst which, has. an upper level at Linto a disengaging space disposed between L and the upper portion of thereactor. In this disengaging space there is a light phase suspension ofcatalyst in gasiform material which decreases in concentration towardsthe top of the reactor, for it is characteristic of this type oftechnique that the main bulk of As is conventional, there is disposed inthe separators 7 through which the gasiform material about to issue fromthe reactor is forced for the purpose of removing entrained catalyst,which removed catalyst is returned to the dense phase bed C by one ormore-dip pipes d. The gasiform material finally emerges from as regardshydrogen requirements for the hydroforming stepor phase.

It is pointed out that hydroforming is an operation conducted atelevated temperatures and pressures in the presence of added hydrogenand a solid contact material wherein the feed stock is a hydrocarbon oilcontaining substantial quantities of naphthenic hydrocarbons which areconverted to the corresponding aromatics by dehydros o Us l y e d orm nsoper ion is. a companied by some isomerization of straight chainparaffins present and isomerization of alkylated S ea -hon naphthenicring compounds such as ethylcyclopentane, to

-a 6-carbon ring such as methylcyclohexane.

.matically thecssential elements of a suitable apparatus I in which apreferred modification 'of'the tion may be carried into effect.

Referring in detail to the drawing l represents, a hydroforining zonecontaining a fluidized bed of catalyst present invenplatinum orpalladium carried on a spacing agent.

the reactor through line 8.

With respect to the catalyst in bed C, it is pointed out that this maybe any conventional reformer catalyst such as a VI group metal oxidecarried on a suitable spacing agent, or it may be a precious metalcatalyst such as In the first class of catalysts are included molybdenumoxide or chromium oxide carried on activated alumina. In the secondclass of catalysts mentioned, the carrier may be also alumina associatedwith a minor amount of silica. In both cases, the catalyst may haveassociated therewith a relatively small amount of hydrogen. fluoride.The present combination may be either of the so-called regenerative typeor it may be the non-regenerative type.

"In the case where the catalyst requires regeneration, the

catalyst may be withdrawn either continuously or periodically andtreated with air or other regeneration gas in conventional apparatus notshown.

Referring again to the product in line 8; issuing from reactor 1, thesame is first fed to a conventional scrubbing means 9 Where it istreated with, say, an oil to scrub out the last traces of catalyst,which may still persist in the "vapors and the oil sluirythus obtainedmay be returned to the bed of catalyst in reactor 1 .via line 9a..

The

7 scrubbed vapors from9 are charged via line 10 to a cooler and 2represents a vessel in which hydrodealkylation of ll'wherein thenormally liquid constituents are condensed ahd the product is thencharged via line 12 into a separator 13.. Bron separator 13 a hydrogenrich gas is withdrawn pverhead vialine 14 and pumped in pump 15 throughline 16 through heat exchanger 17 to line 18 and thence to line 4 forreturn to vessel 1, as previously indicated.

Referring again to separator 13, the liquid product is withdrawntherefrom through line 19 and charged to a fractionating column 20. Fromfractionating column 20, a light hydrocarbon fraction is withdrawnoverhead through line 21 and this fraction may be utilized for blendinginto a motor gasoline, or otherwise disposed of. A second intermediatefraction is taken 011 still through line 22 and this fraction comprisesthe motor gasoline fraction boiling between the light ends, which aretaken off at line 21, and at 300 F.; the heavier material boiling from300 F. to, say, about 450 F. is withdrawn from the bottom side stream ofstill 20 through line 23. Higher boiling polymer products, if any, areremoved through line 23a from bottom of still 20 and are disposed of asfuel oil or otherwise utilized. The material in line 23 contains almostexclusively C8 to C11 alkylated aromatics, and it is one of the mainpurposes of this invention, as previously stated, to dealkylate thesearomatics in the presence of hydrogen to form benzene, toluene andxylenes. This product is withdrawn, as stated, through line 23, thencepassed through valved line 24 and charged to furnace 25 where it isheated to a temperature of about 800 F. or whatever temperature isrequired to control the temperature in reactor 2, but in any case, at atemperature below that prevailing in reactor 2, which it has been notedis a reactor in which the hydrodealkylation reaction occurs, andthereafter withdrawn from the heater -25 through line 26 and charged toline 27 leading into the bottom of reactor 2. Hydrogen-containing gasesfrom line 16 are withdrawn therefrom through valved line 28 andcompressor 28a and also charged into line 27. The

mixture of oil vapors and hydrogen gas passes into the reactor 2 andupwardly through a grid or other foraminous member G1 into contact withthe fluidized bed of powdered material C1, which has an upper densephase level at L1. As usual, the superficial velocity of the gasiformmaterial is maintained so as to form the powdered material into a densefluidized bed. This velocity is of the order of .21.7 ft. per secondwhere the powdered maaterial has a particle size of 100-400 mesh.

Under conditions of temperature, pressure and residence time or feedrate set forth hereinafter, the reaction in vessel 2 occurs and theproduct passes through to a disengaging space in reactor 2 positionedbetween L1 and the top of the reactor. As usual, one or more cycloneseparators 29 are disposed in the upper portion of the reactor for thepurpose of separating entrained powdered material from the gasiformmaterial about to issue from the reactor, and this separated powderedmaterial is returned to reactor via one or more dip pipes d. The crudeproduct is withdrawn from the reactor through line 30 and caused to flowin heat exchange relationship with the hydrogencontaining gas in heatexchanger 17 previously mentioned, and thereafter it is withdrawn fromthe heat exchanger 17 through line 31 and charged to scrubber 32 Whereit is treated with a portion of the heavy ends in line 23, whichheavyends pass from line 23 into line 33 near the top of said scrubber 32,the purpose of the scrubbing being to remove entrained particles ofsolid powdered material. The slurry of oil and powdered material iswithdrawn from scrubber 32 through line 34 and charged to line 26.forreturn to reactor 2. The scrubbed product is withdrawn from scrubber 32through line 35, condensed in a cooler 36, withdrawn from the condenserthrough line 37 and charged to a separator 38. From separator 38, aportion of the gas is withdrawn overhead through line 39 and rejected inpart through line 39a from the present system while the remainder isrecirculated to re- .ac-tor 2 through line 39b, compressor 39c and lines26 and 27. The liquid product is withdrawn from separator 38 throughline 40 and charged to a finishing still 41. From finishing still 41,four fractions are recovered as follows: through line42 hydrocarbongases are recovered, through line 43, a benzene fraction is recovered,through line 44, a toluene fraction is recovered, and finally, throughline 45, a mixture of xylene isomers and heavy higher boiling aromaticsare recovered. These aromatic fractions have a purity of -100% as aboverecovered and without further purification.

Referring to reactor 2, a small percentage of feed in line 27 isconverted to carbon in the reactor. When this amounts to 5-25% of solidscontent in the reactor, a portion is withdrawn through line 47 and freshinert material, such as sand is added through line 46 to restoretheinventory in reactor 2. The carbon may be burned from the materialwithdrawn through line 47 so that the carhon-free solids may be addedthrough line 46, but the method and technique of this carbon burning isnot a part of this invention.

To explain the present invention, the following further information isset forth representing typical operating conditions for obtaining theindicated results:

Conditions in reactor 1 Preferred Range Feed temperature, F 950 850-1,Pressure, p. s. l 200 -50 Temperature, F., in reactor 900 850-975 Spacevelocity, lbs. fcedlhnllb. catalyst 0. 25 0. 15 0. 8 Recycle gas, 0.F./Bb1 3,000 2, DOD-6,000 Catalyst-10% molybdena on activated alumina.

Feed stock to reactor 1 API 48.2 Anil pt 129 I. B. P., F 284 10% 298 50%324 90% 379 F. B. P 412 CFRR octane number 39.2 Aromatics, vol. percent14.6 'Naphthenes vol. percent 46.1 Parafiins 39.3

Product inspection-reactor 1 Liquid yield, C4-EP, vol. percent feed 85CFRR octane number 95 Aromatics, vol. percent 63 Naphthenes 10 Parafiins27 C4300 fraction, vol. percent of feed 45 300+ fraction, feed toreactor 2, vol. percent "Products #051 reactor 2 B n Yie 2 f rqd t 9t eat r 2 "Tolueneyield, 30% Qfproductof reactort 2 In the hydrodealkylationreaction in r eactor 2 about 1500 s. c. f. of hydrogen per barrel offeed is consumed in the highly exothermic reaction of removingsubstantially all of the side chains from the aromatic rings and theaddition of hydrogen to form the 'dealkyl'ated aromatic ring andresultant paraflin products. The exothermic heat of this reaction is inthe order of 500 B. t. u. per pound of liquid feed. It is obvious thatif the feed mixture was brought to the initial reaction temperature ofabout 1200 F. as in the conventional fired tube reactor, a run-awayreaction would occur, the exothermic heat causing a temperature rise ofabout 500 F., or to 1700 R, if cooling were not used. On the other hand,in the fluidized bed of solids here used, the feed mixture thereto neednot be brought to 1200 F., but rather can be introduced at a temperaturelower than the reaction temperature, say, BOW-900 F., and the exothermicheat of reaction is used, aided by the turbulence in the bed, to heatthe feed to reaction temperature. Thus, the temperature in reactor 2 iscontrolled by varying the preheat temperature of the feed.

The invention is not limited to the precise details set forth above.Naturally occurring heavy aromatic type hydrocarbons as keroseneextracts, heating oil extracts, catalytically cracked heating oilfractions and the like may be introduced through line 50 to mix with thehigh boiling hydroforma-te in line 26 to enter reactor 2 through line 27Of course, high boiling hydroformates from other sources may be used andhydrogen rich gases from other hydroformers, say, one operating on lowerboiling stocks, or from other sources may be fed into line 28 via line51 to add to or enrich the hydrogen-containing gas in that line.

With respect to the catalyst that may be employed, it is pointed outthat in addition to molybdenum oxide, chromium oxide, nickel sulfide, ortungsten sulfide, or any of a number of oxides or sulfides of metals ofgroups IV, V, VI, VII and VIII of the periodic system. These catalystsare usually supported on a base or spacing agent and the most commonlyused base is alumina, either of the gel type or precipitated alumina.For example, a modified alumina, made by heat treating hydrated aluminumoxide, has been used as a support or extending agent for the activereforming catalysts mentioned above. Thus, a good catalyst for reformingor hydroforming is one containing about molybdenum oxide supported on analumina base. However, alumina in its various forms is not heatstable,particularly at regeneration temperatures which are of the order of11001400 F. At these temperatures alumina is definitely impaired byprolonged heating, and this impairment is reflected in the loss ofactivity of the catalyst composition of which the alumina is the supportor spacing agent.

With respect to the hydrogen concentration in the recycle gas, it may beof the order of 60-75% hydrogen although, of course, purer hydrogen maybe employed.

It will be understood that the alkylated aromatics which arehydrodealkylated according to the present process may be from anysource. In other words, these alkylated aromatics may be recovered, forexample, from thermal reforming of heavy naphthas, or from any sourcewhere these heavy aromatics would be present. One of the main featuresof the present invention is to provide equipment which will be useful incarrying out the hydrodealkylation, and as hereinbefore pointed out oneof the important aspects of the present invention involves providing asystem which supplies hydrogen necessary in the hydrodealkylationprocess. Specifically, the present invention defines the hydrogennecessary for the hydrodealkylation by hydroforming naphthenic naphtha,which hydroforming operation results in a net production of hydrogenover and above that necessary for the hydroforming operation, and thisexcess hydrogen may be utilized in the hydrodealkylation step of thepresent combination. Another'important aspect of the present inventionresides in the fact that the catalyst in the hydroforming zone and thepowdered solids in the hydrodealkylation zone are in the form offluidized beds which means that the respective beds of powdered materialare maintained at substantially uniform temperatures throughout. This isvery important with respect to the hydroforming operation, which becauseit is a highly endothermic reaction, has heretobefore been carried outin fixed beds of catalyst through which severe temperature dropsoccurred. To counteract this temperature drop through the beds in priorpractice, it was necessary to preheat the feed to temperatures at whichthere was imminent danger of causing thermal cracking of said feed. Thepresent technique permits much lower preheat of the feed to thehydroforming zone and consequently reduces thermal cracking in thepreheating furnaces.

Numerous modifications of the present invention will be obvious to thosewho are skilled in the present art without departing from the spirit ofthe invention.

What is claimed is:

1. The method of producing high octane gasoline and aromatics of highpurity which comprises subjecting a naphtha containing naphthenes whichare predominantly C9-C11 hydrocarbons and boiling substantially withinthe range of 250450 F. to a hydroforming operation in the presence of afluidized bed of hydroforming catalyst, recovering a hydroformed productfrom the hydroforming step, recovering a gas rich in hydrogen from thesaid hydroforming step separating a motor gasoline fraction from saidhydroformed product, recovering high boiling alkylated aromatics fromsaid hydroformed product, preheating said aromatics to a temperature offrom about 800 -900 F. and thereafter subjecting said aromatics tohydrodealkylation in the presence of a fluidized bed of powdered inertnon-catalytic material and in the presence of added hydrogen recoveredfrom the said hydroforming step and recovering therefrom benzene,toluene and xylene isomers.

2. The method set forth in claim 1 in which the catalyst is a VI groupmetal oxide carried on alumina base.

3. The method set forth in claim 1 in which the powdered material issand.

4. The method of producing high octane gasoline and aromatics whichcomprises subjecting a naphtha containing naphthenes which arepredominantly C9-C11 hydrocarbons having an end boiling point above thegasoline boiling range to the influence of heat and pressure in thepresence of a fluidized bed of a hydroforming catalyst in a hydroformingzone, feeding a hydrogen-containing gas to said hydroforming zone,permitting the reactants to remain resident in the reaction zone for asufficient period of time to effect the desired conversion, withdrawingthe product from the hydroforming reaction zone, recovering ahydrogen-containing gas from the product withdrawn from the hydroformingreaction zone, separating for product a hydroformate boilingsubstantially within the motor gasoline boiling range, recovering aresidual product containing high boiling alkyl aromatics, preheatingsaid residual product to a temperature of from about 800900 F. andthereafter subjecting said residual material at hydrodealkylationtemperatures and pressures to contact with a powdered inertnon-catalytic material in the form of a fluidized bed and added hydrogenrecovered from the said product Withdrawn from the hydroforming reactionzone for a sufiicient period of time to effect dealkylation of saidresidual material and recovering an aromatic product containing benzene,toluene and xylene.

(References on following page) References Cited in the file of thispatent UNITED STATES PATENTS Odell Dec. 18, 1934 Atwell Oct. 14, 1941 5Welty July 10, 1945 Oblad Aug; 21, 1945 Ashmore et al Feb. 19, 1946Haensel et a1. June 24, 1947 Beckberger Apr. 6, 1954 10 Friedman Ian.25, 1955 8 OTHER REFERENCES Yuknevski: Chem. Abstracts, vol. 23, pages377-8 (1929).

Oda: J. Soc. Chem. Ind., Japan (1931), vol. 34, also reported in Ellis,Chemistry of Petroleum Derivatives (1934), pages 88-89. Published by theChemical Catalog Co., 1110., N. Y., N. Y.

1. THE METHOD OF PRODUCING HIGH OCTANE GASOLINE AND AROMATICS OF HIGHPURITY WHICH COMPRISES SUBJECTING A NAPHTHA CONTAINING NAPHTHENES WHICHARE PREDOMINANTLY C9-C11 HYDROCARBONS AND BOILING SUBSTANTIALLY WITHINTHE RANGE OF 250*-450*F. TO A HYDROFORMING OPERATION IN THE PRESENCE OFA FLUIDIZED BED OF HYDROFORMING CATALYST, RECOVERING A HYDROFORMEDPRODUCT FROM THE HYDROFORMING STEP, RECOVERING A GAS RICH IN HYDROGENFROM THE SAID HYDROFORMING STEP SEPARATING A MOTOR GASOLINE FRACTIONFROM SAID HYDROFORMED PRODUCT, RECOVERING HIGH BOILING ALKYLATEDAROMATICS FROM SAID HYDROFORMED PRODUCT, PREHEATING SAID AROMATICS TO ATEMPERATURE OF FROM ABOUT 800*-900*F. AND THEREAFTER SUBJECTING SAIDAROMATICS TO HYDRODEALKYLATION IN THE PRESENCE OF A FLUIDIZED BEDOFPOWDERED INERT NON-CATALYTIC MATERIAL AND IN THE PRESENCE OF ADDEDHYDROGEN RECOVERED FROM THE SAID HYDROFORMING STEP AND RECOVERINGTHEREFROM BENZENE, TOLUENE AND XYLENE ISOMERS.